1. Field of the Invention
The present invention relates to an information processing apparatus for effecting writing or reading-out of information by physical interaction of plural probes and a recording medium, and a method therefor.
2. Related Background Art
Recently, scanning tunnelling microscope (hereinafter referred as STM) [G. Binnig et al., Phys. Rev. Lett., 49, 57 (1982)] capable of directly observing electron structure of surfacial atoms of a conductive material has been developed, thus the measurement of the real space image is possible with a high resolving power, both in the monocrystalline and amorphous substances.
The STM is based on a phenomenon that a tunnelling current is generated by Tunnelling effect when a metal probe (probe electrode) and a conductive substance are brought to a small distance in the order of 1 nm, with a voltage applied therebetween. The current is extremely sensitive to the variation in a distance between them. By moving the probe in scanning motion, while maintaining the tunnelling current constant, there can be read various information concerning the entire electronic cloud in the real space. In this case the resolving power in the direction along the surface of the substance is in the order of 0.1 nm.
Consequently, the principle of the STM sufficiently enables information recording and read-out of a high density in the atomic (sub nanometer) order. For example, the Japanese Patent Laid-open Application No. 61-80536 discloses a recording/reproducing apparatus which records information by removing atomic particles absorbed on the surface of a medium by means of an electron beam or the like and reproduces the recorded data by STM.
Also there are proposed methods of effecting the data recording and reproduction by the STM, utilizing a thin film of a material having a memory effect for the current-voltage switching characteristics, such as an organic compound having .pi.-electrons or a chalcogenide compound (Japanese Patent Laid-open Application Nos. 63-161552 and 63-161553). This method enables recording and reproduction of a large capacity as large as 10.sup.12 bit/cm.sup.2 for a recording pit size of 10 nm. Also for the purpose of miniaturization, there is proposed an apparatus of forming plural probes on a semiconductor substrate and achieving the recording by displacing a recording medium opposed thereto (Japanese Patent Laid-open Application No. 1-196751). For example, a combination of a multiple probe head having 2,500 probes arranged in a 50 .times.50 matrix on a silicon chip of 1 cm.sup.2 and a material having the above-mentioned memory effect can achieve recording and reproduction of digital data of 400 M bits per probe, or 1 terabits in total.
On the other hand, in the conventional information recording/reproducing apparatus utilizing the principle of STM, there has been given relatively little consideration on the position control (tracking) of the 10 probe, serving as recording-reproducing pickup, on the recording medium. For this purpose, for example, there has been proposed a method of forming a tracking groove or embedding a tracking line on the recording medium, and causing the probe to scan the recording medium to effect the recording and reproduction (Japanese Patent Laid-open Application Nos. 1-107341 and 1-133239).
However, there have been present following drawbacks in the information processing in the recording and reproduction by combining a multi-probe head having plural probes and a recording medium opposed thereto.
In case of information recording on a medium with a multi-probe head, the information of a series is distributed among plural heads in order to achieve high-speed recording. Also the reproduction is achieved by converting the data, reproduced in parallel by plural heads, into serial data.
Also the medium is provided with a tracking groove, and the timing of recording or reproduction is determined by the timing of detection of the tracking groove.
However, in case of a multi-probe head, the timings of detection of the tracking groove by the probes are different for example by the expansion or contraction, such as thermal expansion, of the probes or by fluctuation in the precision of preparation of 10 the tracking groove. Consequently, if the detection timing of a certain probe is utilized for determining the timings of recording or reproduction of other probes, there will result in drawbacks of deteriorated precision in the conversion of the parallel reproduced data into serial data, or mutually unaligned record start positions among the probes, leading to the deteriorated precision in the conversion.